نوع مقاله : علمی-پژوهشی

نویسنده

• اسدالله فلاحی

استاد مؤسسه پژوهشی حکمت و فلسفه ایران

چکیده

در مقالة دیگری نشان داده‌ام که ابن‌سینا گزاره‌های حملی را «متفاوت» و «نااین‌همان» اما «هم‌ارز» با گزاره‌های شرطی می‌داند. مسئلة این مقاله آن است که منطق‌دانان مسلمان پس از ابن‌سینا دربارۀ اینکه گزاره‌های حملی و شرطی «این‌همان» هستند یا صرفا «هم‌ارز»، چه نظراتی داده‌اند. با بررسی آثار بسیاری از منطق‌دانان پیرو ابن‌سینا، این نتایج به دست آمد: (1) سهروردی، فخر رازی، خواجه نصیر و قطب الدین رازی بر خلاف نظر ابن‌سینا به «این‌همانی» حملی و شرطی گرویدند؛ (2) خونجی، سمرقندی، میرداماد و ملاصدرا با رد نظریة «این‌همانی» از نظریة «هم‌ارزی» ابن‌سینا دفاع کردند؛ (3) در کنار این مباحث منطقی، ادیبانی مانند سکاکی، و به پیروی از اوتفتازانی، تقریر جدیدی از نظریة «این‌همانی» میان حملی و شرطی ارائه کردند و مقدم شرطی را بخشی از محمولِ تالی و قیدی از قیود آن دانستند.

کلیدواژه‌ها

• حملی
• شرطی
• موضوع
• محمول
• مقدم
• تالی

موضوعات

• فلسفه

عنوان مقاله [English]

Avicennian logicians on the conversion of categorical propositions to conditional ones

نویسنده [English]

• Asadollah Fallahi

Professor in Iranian Institute of Philosophy

چکیده [English]

Abstract
In another article, I have shown that Avicenna regards categorical propositions as “different” and “not identical,” yet “equivalent” to conditional propositions. In this article, I demonstrate that Arabic logicians after him disagreed on whether categorical and conditional propositions are “identical” or merely “equivalent.” Unlike Avicenna, Suhrawardī, Fakhr al-Dīn al-Rāzī, Naṣīr al-Dīn al-Ṭusī, and Quṭb al-Dīn al-Rāzī accepted the “identicality” of categorical and conditional propositions, while Khūnajī, Samarqandī, Mīrdāmād, and Mulla Ṣadrā defended Avicenna’s theory of “equivalence” by rejecting the theory of “identicality.” Alongside these logical discussions, linguistic scholars such as Sakkākī, and following him, Taftāzānī, presented a new version of the theory of “identicality” between categorical and conditional propositions, considering the antecedent of a conditional as a part of the consequent’s predicate and as one of its adverbs or modifiers.
Keywords: Categorical, Conditional, Subject, Predicate, Antecedent, Consequent.
 
Extended Abstract
Introduction
On the transformation of categorical propositions into conditional ones and vice versa, in another article I have shown that Avicenna accepts these transformations in one sense and rejects them in another. According to him, categorical and conditional propositions are “equivalent” but not “the same.” The statement “Every human is an animal” does not mean “If this is a human, then it is an animal,” but it is equivalent to it, in the sense that whenever one is true, so is the other.
 
Materials & Methods
Now, the question of this article is what perspectives Muslim logicians, followers of Avicenna, have taken regarding the equivalence of categorical and conditional propositions or the transformation of one into the other. The significance of this issue is that in modern logic, universal propositions are transformed into conditionals while particular propositions into conjunctions, and it is clear that the views of Muslim logicians in this regard can lead to valuable comparative discussions between Avicennan and modern logics. In this article, I will show that Muslim logicians have been divided into several different groups and have presented views, some of which have not been previously found in Avicenna or discussed even in modern logic.
 
Discussion & Result
By examining the views of Muslim logicians after Avicenna, we conclude that they can at least be divided into three groups: 
- The first group, containing Shams al-Dīn al-Suhrawardī and Fakhr al-Dīn al-Rāzī, adhere to the theory of “identity” between categorical and conditional propositions, thereby they oppose Avicenna. 
- The second group, containing Afḍal al-Dīn al-Khūnjī, Shams al-Dīn al-Ṣamarqandī, Mīr Dāmād, and Mullā Ṣadrā, revert to Avicenna’s theory of “equivalence” and oppose the theory of “identity.” 
- The third group, starting from Al-Sakkākī and following Al-Taftāzānī, consider the antecedent of a conditional as a part of its consequent; and in this new manner, they transform conditional propositions into categorical ones. This third group can also be regarded as proponents of the theory of “identity” between categorical and conditional propositions, except that here the positions of the antecedent and consequent change. In the view of the first group, the antecedent and consequent turn into the subject and predicate, while the conditional operator “if” transforms into terms like “entails” or “implies” and thus returns to the consequent. However, from the perspective of the third group, the antecedent, together with the conditional operator, becomes part of the predicate of the consequent.
Before these three groups, Bahmanyār, the most prominent student of Avicenna, transforms repetitive (istithnāʾī) conditional syllogisms to categorical ones, which is a complete innovation that, surprisingly, was not continued after him. Before him, his master Avicenna had referred connective (iqtirānī) conditional syllogisms to categorical ones but had not spoken of referring the repetitive (istithnāʾī) conditional syllogisms to categorical ones.
No research has been conducted on the subject of this article aside from the three works mentioned below: 
Bahmanyār proposed the following repetitive (istithnāʾī) conditional Modus Tollens syllogism as a categorical one of the second figure:
 
“If a human is braying, then a donkey is speaking. 
But the donkey does not speak. 
Therefore, the human does not bray.”
 
Bahmanyār analyzes the syllogism as follows:
 
“every time when a human is braying, is a time when a donkey is speaking. 
Now is not the time when the donkey speaks. 
Therefore, Now is not the time when the human brays.”
 
Here is a problem: in the Avicennan logic, a conditional with false antecedent and consequent is false. So how can Bahmanyār’s conditional be true while it has false antecedent and consequent? An answer is that we can take Bahmanyār’s conditional as truth-functional material implication. The author elsewhere showed that the material implication had been used by Avicennan logicians, though they couldn’t discuss it systematically (Fallahi 2009, Fallahi 2011: 131-135).
Ahmad Ahmadi, in his article “The Conditional Proposition is the Same as the Categorical Propositions,” and also in his book Substrata of Knowledge, in Chapter Ten titled “Structure and Nature of Conditional Propositions,” addresses the subject of this article and examines the views of al-Sakkākī and al-Taftāzānī but does not discuss other Avicennian logicians (Ahmadi 2001, Ahmadi 2009). 
Additionally, the present author, in an article titled “Transformation of Categorical Propositions into Conditionals According to Avicenna,” has focused solely on Avicenna’s views on this topic (Fallahi 2024), and the present article aims to explore the perspectives of other followers of Avicenna in detail.
 
Conclusion
From the above, it becomes clear that Muslim logicians after Avicenna can be divided into at least five groups: 

Those who generalize the equivalence of categorical and conditional propositions to that of connective conditional syllogisms and repetitive conditional syllogisms (Bahmanyār).
Those who, in addition to equivalence, assert the “identity” of categorical and conditional propositions (al-Dīn al-Suhrawardī and Fakhr al-Dīn al-Rāzī (in one topic), Akhundi Khurasani, and Naʾini).
Those who deny the theory of “equivalence” altogether (Qutb al-Dīn al-Rāzī, in another topic).
Those who reject the theory of “identity” and revert to Avicenna’s theory of “equivalence” (Afḍal al-Dīn al-Khūnjī, Shams al-Dīn al-Ṣamarqandī, Mīr Dāmād, and Mullā Ṣadrā).
Those who regard the entire antecedent as a modifier of the consequent’s predicate (Al-Sakkākī, Al-Taftāzānī, Akhūnd Khurāsānī, Nāʾīnī, Ahmad Ahmadi).

This categorization shows that, contrary to expectations, most Avicennian logicians at least accept the equivalence between categorical and conditional propositions, and some even believe in their identity—an opinion that has been explicitly and emphatically stated in modern logic. Therefore, from this perspective, Avicennan and modern logics have had more or less similar views, although of course there have always been and still are disagreements in details.

کلیدواژه‌ها [English]

• categorical
• conditional
• subject
• predicate
• antecedent
• consequent